Neurophilosophy

The mirror movement mutation

MIRROR movements are involuntary movements that mimic, and occur simultaneously with, voluntary movements on the opposite side of the body. The movements are known to occur because of a failure in communication between the two sides of the nervous system. They are thought to be normal during infancy and early childhood, but usually diminish with age and disappear altogether by the age of 10, following maturation of the corpus callosum, the massive bundle of nerve fibres connecting the left and right hemispheres of the brain.

A large genetic study published online in the journal Science now shows that mirror movements are caused by a single genetic mutation. The mutation is located within a gene that encodes a well-known protein involved in guiding growing nerve fibres to their proper destination during development, and gives rise to mirror movements because the connections between the two brain hemispheres fail to form properly.

Mirror movements are uncommon in adults, but they are known to be heritable, and can occur sporadically for a wide variety of reasons. They are a symptom of Parkinson’s Disease, cerebral palsy, schizophrenia and obsessive compulsive disorder; they can occur during epileptic seizures, or following a stroke or some other insult to the brain; they are also associated with alien hand syndrome, and can even occur in otherwise healthy people during prolonged physical exertion or in severe fatigue.

The movements almost always affect the arms and hands, but legs can also be affected. They are usually relatively subtle, so that individuals can find them to be inconvenient and embarrassing but not disabling. Their subtlety can be seen in this film clip of a 21-year-old soldier, who was banned from using ammunition by his senior officers, because of fears that he might cause a firearm-related accident. When he flexes the fingers of his right hand, as if to pull a trigger, the fingers on his left hand perform similar but more subtle movements:



Myriam Srour of the University of Montreal and her colleagues previously described two large families – one French-Canadian, the other Iranian – that contain members affected by mirror movements. The researchers discovered the mutation by performing a genome-wide association study, which is designed to identify genetic variants associated with a particular condition, and is performed by comparing the genomes of affected individuals with those of large numbers of healthy controls.

All of the affected family members were found to harbor the same point mutation in the Deleted in Colorectal Cancer (DCC) gene, which encodes a receptor for a classical axon guidance molecule called Netrin-1. The mutation was not found in unaffected family members, or in some 1,300 unrelated controls. The researchers then isolated the gene from from the affected individuals, and found that the mutation produces a shortened form of the DCC protein which is missing the Netrin-1-binding region.

First identified almost 20 years ago, DCC and Netrin-1 are highly conserved in evolution, and their functions are very well characterized. Versions of both genes are found in fruit flies, nematode worms and vertebrates, and the proteins they encode serves the same function in all of these organisms. One important function of the interaction between DCC and Netrin-1 is to guide growing nerve fibres towards the midline of the nervous system during embryonic development, and to help them make steering decisions once they reach it.

DCC is found in the extending tips of the fibres, while Netrin-1 is synthesized and secreted by midline cells. The tips of the fibres are attracted to the Netrin signal, growing towards the areas where it is most highly concentrated, so that the nerve fibres cross from one side of the nervous system to the other. The interaction between DCC and Netrin-1 is therefore important for the proper formation of the commissures, the fibre tracts that connect the left and right sides of the nervous system. In mammals, the largest of these is the corpus callosum, but there are several smaller ones on the brain, and even smaller ones at regular intervals along the length of the spinal cord. Given its well established role in commissure formation, the finding that DCC mutations result in mirror movements are not particularly surprising, but the results do confirm that the protein plays the same role in the human nervous system as it does in other organisms.


Srour, M., et al. (2010). Mutations in DCC Cause Congenital Mirror Movements. Science 328: 592-592. DOI: 10.1126/science.1186463.

Comments

  1. #1 Crazy Mermaid
    May 1, 2010

    This article led me to your Body Swap Illusion article thought your Alien Hand syndrome reference. As usual, both of these articles are nothing short of Fascinating!

  2. #2 Stagyar zil Doggo
    May 4, 2010

    Deleted in Colorectal Cancer (DCC) gene

    Could you clarify what role it plays in Colorectal Cancer, and if this role is related to its function in axon guidance.

  3. #3 Mo
    May 6, 2010

    @Stagyar: DCC contributes to various types of cancers, including colorectal cancer. It’s exact role is not clear. It may be a tumour suppressor gene that is epigenetically silenced in cells that become cancerous. Given its role as an axon guidance molecule, it may also mediate in cell movements and therefore be involved in metastasis.

  4. #4 Stagyar zil Doggo
    May 13, 2010

    Thx.

  5. #5 katie
    May 17, 2010

    im 17 and i just found out what this was called 3 days ago. this happens to me from my shoulder to my fingers and its difficult to do alot of things.

  6. #6 K. Knight
    June 27, 2010

    Very interesting article. I am 54 and I have had mirror movements in my hands since I can remember. My mother has it as well. It seems a bit more controlable as I have grown older, but shows up worse when I’m tired. I have adapted as anyone with a slight disability usually would. Things as simple as carrying something heavy with one hand and trying to open the other hand to assist in the process are difficult, but managable. I have 5 grandchildren now and with each one born I wonder if they will show the signs of MM. So far no one else in the family has MM. I am still eager to hear more about MM.

  7. #7 mark
    August 17, 2010

    im 18 and i still have this problem. i wanna play instruments like the piano and i cant because of this. is there a way to get rid of this?

  8. #8 bob
    August 22, 2010

    i too have had mm for as long as i can remember…i am 57 and it has only been a mild embarrassment at times…

  9. #9 Liz Franz
    November 16, 2010

    Hello all people with congenital mirror movements,

    It was wonderful reading your interesting entries. I am a researcher of congenital mirror movements and I would love to be contacted by you if you have the time. I’m at franz.liz@gmail.com.

    Thanks!

  10. #10 MJ
    December 16, 2010

    I’m 46 and have had this all my life as well. To those of you who are younger and concerned about limitations – that is completely up to you. If you take no responsibility for learning new ways of doing things, then you will be limiting yourself, not limited by the differability (as opposed to disability).

    I can type faster than most people because I type with both hands hovering *above* the keyboard, so that only the intended finger strikes the intended key.

    You can play piano – it takes more practice, you’ll have to teach each hand it’s part separately, and for some movements you would simply strike a commmon left-hand chord. But it can be done (I don’t find it a good use of my time, personally).

    Be careful using a knife to peel items (I just don’t, easy). When entering a door with items in hand, set them down, open the door, pick them back up. It’s just a part of life.

    Just don’t make a big to-do about it and for the most part, people won’t usually notice, and you won’t be any more limited than you choose to be.

    By the way, I have *no* other relatives, past, present or children/neices/nephews who have this. Also, it in no way impairs my mental or social functions. So – to those who are young and worried about it – don’t. It’s not a big deal.

  11. #11 Deanna
    January 28, 2011

    I have also learned a variety of ways to deal with my MM problems, and sometimes it means closing my left hand into a fist or gripping something tightly while doing detailed work with my right hand (mine only works one direction unless I am very tired).
    Hovering over the keyboard is also something that I do and it makes a big difference.

    Also, it is kind of fun to show people at the kind of really boring parties that I attend…

  12. #12 joanne sevigny-stone
    February 15, 2011

    I am 57 and I have MM. Interesting info. My mother passed this trait on to me, I passed it on to my daughter. My niece also has MM, In our family this so called disorder only affects the females. However my sister does not suffer from this…Is it more promident in the femle gender and if so why?

  13. #13 Liz
    April 25, 2011

    hello All,

    I’m still interested in hearing from you, as I am a researcher of congenital mirror movements. If you want to learn more about what we are doing, and/or possibly participate in our study (over mail) I’d really appreciate hearing from you: franz.liz@gmail.com

    Thanks. All the best, Liz

  14. #14 Isaac
    June 4, 2011

    Hey, I’m 21 and had it since birth. i have learnt to control it for the most part although it does show when I’m tired. In my family of Seven ( 2 parents, 5 kids (no im not a parent)) only my father, me and one of my brothers seems to have this. Not really hard to live with just annoying at times. Good luck with your reaserch Liz.

  15. #15 sonata
    June 18, 2011

    sveiki, rasau jums, liz. norejau issiusti jums laiska, bet adresas jusu neteisingas. mano sunui bus 2 metai amziaus. jo igimti veidrodinaii ranku judesiai, veluoja motorika, zemas raumenu tonusas

  16. #16 sonata
    June 18, 2011

    Hello, I am writing to you, Liz. wanted to send you a letter, but your address is incorrect. my son is 2 years of age. his innate veidrodinaii hand movements, delayed motility, low muscle tone

  17. #17 Terri
    June 21, 2011

    I am 52 years old and I have had this my whole life. My father had it, my brother has it, one of his sons has it, my son has it and now his 11 month old daughter has it. It is strickly with our hands and fingers. None of us has out grown it and it hasn’t gotten any better as we have aged. It is very frustrating at times and can limit what we can do (like playing the banjo…it can’t be done). I am so happy to hear that we aren’t the only family with this problem. At least I now know what it is and can explain it to my son as he is not happy that his daughter has it. It can be very embarrassing to say the least.

  18. #18 Seth
    June 23, 2011

    I’m 28 and I’ve had this as long as I can remember. The mirroring display occurs only in my fingers, and not in my wrists, elbows, etc, and is more dominant in my middle fingers, and less and less dominant towards the outer fingers.

    The mirroring is stronger if the muscles in my fingers are more engaged, like when carrying something heavy, crossing the monkey bars (which I’ve never done), writing/coloring, turning a doorknob, or playing the guitar, which, not to be arrogant, I do very well. It was a slight undertaking to keep my right hand fingers from hitting the strings due to movement from the left hand on the fret board. It actually looks pretty funny when I do a trill (the alteration of the left hand index and middle finger on one string) because my right (picking) hand fingers are fluttering away, lol.

    I also teach guitar, and use this as a “If I can do it, YOU can do it” motivation story to my students.

    Oh… and I can also hold a pen in each hand and sign my name at the same time, only the left hand is a perfect mirror image of my signature!

  19. #19 julie leach
    August 16, 2011

    hi i am a mother of a almost 11 year old daughter i have known that when she moves one hand her other hand moves too it has become a issue this past few weeks when she decided that she wanted to join cheerleading she tries to do their hand movements and she does them quite well with the exception that so does her other hand she came to me yesterday and said someone was making fun of her because of it… my heart broke for her… her father was born with it also… we recently found out when her father (my husband) went for a mri due to headaches that there is a sac on the back of his head that is hydrocephulus and has nerves wrapped around it i just read that their was a little boy with the same issue could this also have caused this??? i want to beable to give my child a answer is their something that can be done somehow to fix it… please help me to help my child understand this…

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